Correlation Between Muscle Fiber Cross-Sectional Area And Strength Gain Using Three Different Resistance-Training Programs In College-Aged Women

Abstract

The purpose of this investigation was to report the formerly uninvestigated relationship between previously reported muscle fiber cross-sectional area and muscle performance changes for college-aged women using one of three resistance-training methods. Thirtyfour healthy adult females (21.1 ± 2.7 y) were randomly divided into four groups: control (C), traditional strength training (TS), traditional endurance training (TE), and low velocity training (LV). Workouts consisted of three exercises: leg press, back squat, and knee extension. Each subject was pre- and post-tested for 1 Repetition Maximum (1-RM), and relative muscular endurance (60% 1-RM). Pre- and post-training vastus lateralis muscle biopsies were also analyzed for fiber cross-sectional area (CSA). For each training session, TS trained at 6-10 RM (6-10 repetitions to failure) with 1-2 s concentric/1-2 s eccentric; TE trained at 20-30 RM (1-2 s concentric/1-2 s eccentric); and LV trained at 6-10 RM, with 10 s concentric/4 s eccentric. Both TE and LV trained at the same relative intensity (40-60% 1RM), whereas TS trained at 80-85% 1RM. Each training group attended a minimum of 16 out of 17 training sessions in which the exercises were performed to fatigue for each of 3 sets. For this investigation, the percent change in strength (%strength) was averaged across the three exercises, as was the percent change in number of repetitions (%reps) and volume (%vol) performed during the muscular endurance test (volume was calculated as load times repetitions performed). Significance was set at an alpha of 0.05. The %strength was significantly greater for TS compared to all other groups and also for LV as compared to C. The %vol was significantly greater for TS as compared to LV and C, and LV and TE as compared to C. The %reps was significantly greater for TE as compared to C. As previously reported, percent change in CSA for type I, IIa, and mean CSA was significantly greater for TS as compared to all other groups, and for type IIx, TS was significantly greater than C only. The %strength was significantly correlated with percent change in CSA for type I, IIa and mean CSA, %vol was correlated with percent change in CSA for type IIa and mean CSA, and there were no significant correlations between %reps and any percent change in CSA. Strength gains are correlated with increases in type I and IIa, as well as mean CSA. Changes in muscle endurance as found by changes in number of repetitions at a relative % 1-RM are not correlated with changes in CSA. However, when using volume instead of repetitions, muscle endurance is correlated to muscle fiber CSA changes. It appears that the higher load used with TS is associated with the highest percent increases in both strength and muscle fiber CSA, and is therefore the most beneficial training method of the three presented if considering these outcomes.